|Publication number||US6958983 B2|
|Application number||US 09/738,067|
|Publication date||Oct 25, 2005|
|Filing date||Dec 15, 2000|
|Priority date||Jan 25, 2000|
|Also published as||DE60134951D1, EP1234461A1, EP1234461B1, US20020015392, WO2001056315A1|
|Publication number||09738067, 738067, US 6958983 B2, US 6958983B2, US-B2-6958983, US6958983 B2, US6958983B2|
|Inventors||Niilo Musikka, Lars Lindén, Lennart Rinnbäck, Peter Galyas|
|Original Assignee||Telefonaktiebolaget Lm Ericsson (Publ)|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (11), Non-Patent Citations (1), Referenced by (21), Classifications (16), Legal Events (3)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This Application for Patent claims the benefit of priority from, and hereby incorporates by reference the entire disclosure or, co-pending U.S. Provisional application for patent Ser. No. 60/177,819, filed Jan. 25, 2000.
This Application for Patent also incorporates by reference the entire disclosure of commonly-assigned, co-pending U.S. application for patent Ser. No. 09/494,606, filed Jan. 31, 2000.
1. Technical Field of the Invention
The present invention relates in general to the mobile telecommunications field and, in particular, to a method and system for optimal routing of calls in a Base Station System (BSS).
2. Description of Related Art
Each BSC in a GSM network can control a plurality (typically hundreds) of radio cells. In other words, each BSC (e.g., 16) interworks with a plurality (hundreds) of BTSs via respective Abis interfaces. Each BTS (e.g., 14) is responsible for the transmission and reception of radio signals over an air interface, Um, in one cell. Consequently, the number of cells in a GSM BSS is equal to the number of BTSs in that BSS. As such, the BTSs are geographically distributed to provide adequate radio coverage of a BSC area, which forms part of a GSM Public Land Mobile Network (PLMN).
Additionally, the BTSs provide the capacity to carry a plurality of connections (calls) between Mobile Stations (MSs) (e.g., 22) and respective BSCs. In the GSM, each BTS is equipped with one or more Transceivers (TRXs). Each such TRX (not shown) is capable of handling eight timeslots of a Time Division Multiple Access (TDMA) frame. Furthermore, each such timeslot can be assigned different combinations of logical channels, such as, for example, Broadcast Control Channels (BCCHs) and Common Control Channels (CCCHs), Stand-alone Dedicated Control Channels (SDCCHs), and Traffic Channels (TCHs).
A second node connected to the IP network 108 is a GateWay (GW) 104. The GW 104 can be used to terminate the A-interface. Also, the GW 104 can perform a conversion from one protocol (e.g., SS7 protocol) to another protocol (e.g., Transmission Control Protocol (TCP)/IP). The GW 104 can also include a Media GW (MGW) which functions similarly to existing Transcoder Controllers in an Ericsson implementation of the GSM model. The MGW (not shown) includes a pool of Transcoder/Rate Adaptor (TPA) devices (not shown), which, when allocated, are connected to the A-interface. However, the IP network (e.g., GSM) side of the TRAs in the MGW are connected to respective UDP ports. Preferably, the GW 104 is connected to the IP network 108 via a separate router (not shown).
A third node connected to the IP network 108 is a Radio Network Server (RNS) 106. The RNS 106 functions similarly to a BSC used for implementing a GSM model. A primary difference between the RNS 106 and a BSC is that the RNS does not switch payloads and does not include a Group Switch (GS). As such, the RNS 106 preferably carries signalling only, and includes a pool of processors (e.g., the number of processors determined by capacity requirements). The RNS 106 provides a robust, general purpose distributed processing environment, which can be based on a standard operating system such as, for example, SUN/Solaris™. The RNS 106 can serve one or more logical BSCs and is preferably connected to the IP network 108 via a separate router. As such, the payload can be routed directly between the GW 104 and RBS 102, without passing through the RNS' 106 processors. The A-interface signalling is routed between the RNS 106 and GW 104.
As illustrated by the BSS 200 shown in
In accordance with a preferred embodiment of the present invention, a method and system are provided for optimal routing of calls in an IP-based BSS, whereby a plurality of new messages are introduced on the A-interface. One such message informs the BSS that the CICs included in the message can be connected to the BSS to provide optimal routing of one or more calls. Another such message informs the BSS that the CICs included in the message are to be restored as separate CICs on the A-interface. The provision of such messages overcomes the above-described and other related disadvantages of the existing and developing BSS implementations.
An important technical advantage of the present invention is that the tromboning problems associated with existing BSS implementations are resolved.
Another important technical advantage of the present invention is that no circuit-switching procedures are involved, which greatly simplifies the resolution of problems with the existing BSS implementations.
A more complete understanding of the method and apparatus of the present invention may be had by reference to the following detailed description when taken in conjunction with the accompanying drawings wherein:
The preferred embodiment of the present invention and its advantages are best understood by referring to
Essentially, in accordance with a preferred embodiment of the present invention, a method and system are provided for optimal routing of calls in an IP-based BSS, whereby a plurality of new messages are introduced on the A-interface. One such message informs the BSS that the CICs included in the message can be connected to the BSS to provide optimal routing of one or more calls. Another such message informs the BSS that the CICs included in the message are to be restored as separate CICs on the A-interface. The provision of such messages overcomes the above-described and other related disadvantages of the existing and developing BSS implementations.
Specifically, in accordance with the preferred embodiment of the present invention, two new messages can be introduced for use in a BSS on an A-interface. One such message, hereinafter referred to as a “Join CIC” message, for example, includes IEs with information about which CICs and Signalling Connections belong to a single conversation, and thus the associated call can be routed in an optimal fashion. A second such message, hereinafter referred to as a “Restore CIC” message, for example, includes IEs with information about which CICs are to be restored separately on the A-interface. For this exemplary embodiment, the MSC sends a “Join CIC” message to the BSS, in order to inform the BSS that the CICs included in the message can be connected in the BSS in a manner that will provide optimal routing. However, the signalling connections towards the MSC should be maintained, so that any of the MS' parties can be capable of invoking subscriber services, for example, if required.
A result of executing the “Join CIC” procedure in the above-described fashion is shown in FIG. 5. As illustrated in
If the MSC 312 desires to restore the original setup (e.g., as shown in FIG. 4), the MSC can send a “Restore CIC” message to the BSS 300. In this case, the RNS 307 instructs BTSa 306 to start sending the speech packets to IP/port-a2 303 b, and also instructs BTSb 308 to start sending the speech packets to IP/port-b2 305 b. The RNS 307 instructs the GW 311 to resume sending speech packets for the two connections IP/port-a2 303 b and IP/port-b2 305 b.
Typically, in most cases, the above-described restoration procedure (instigated by the “Restore CIC” message for the preferred embodiment) should not be needed. Therefore, in most cases, the optimal routing procedure (instigated by the “Join CIC” message, for the preferred embodiment) can be maintained until the ongoing call is cleared from the MSC 312. Nevertheless, an issue that arises in this regard is that when speech information is conveyed directly between BTSs (and the MSs), the same speech coding should be employed in both directions. As such, in order to reach agreement about common speech coding in this regard, negotiations between the two MSs and the BSS have to be conducted. Notably, however, the European Telecommunications Standards Institute (ETSI) has set forth rules for conducting such negotiations.
For this exemplary embodiment, the connection path in the IP network 309 between the transcoders in the GW 311 and the BTSs 306 and 308, the transcoders themselves, and appropriate communication resources in the MSC 312 are maintained during a call during execution of a “Join CIC” procedure for optimal routing. The purpose for this practice is to make sure that these resources remain available in the event that the original connection path has to be re-established. (Note that a connection path in an IP network is actually reserved bandwidth and not a physical path, as in a circuit-switched network.) If the MSC 312 desires to intervene in a call (e.g., a third party is to be connected to the call), the MSC again informs the RNS 307 by sending a “Restore CIC” message to the RNS so that the RNS can reconnect the MSC into the call. The re-connection can be made by replacing existing IP addresses with appropriate new IP addresses in the BTSs 306 and 308.
Essentially, for this embodiment, a handover procedure for directly connected BTSs (e.g., during execution of a “Join CIC” procedure) can also be accomplished by replacing existing IP addresses with appropriate new IP addresses. For a relatively short duration during the handover procedure, a BTS sends speech packets to both an “old” and “new” BTS. When the handover procedure is completed, the “old” BTS can be removed from the call. As such, once a mutual connection is established between the two BTSs upon completion of the handover procedure, the “old” BTS can be completely disconnected from the call. However, if the handover procedure is unsuccessful, the “new” BTS can be removed from the call and the original connection can continue to proceed. If a subscriber leaves the RNS's area, the remaining connection is disconnected from the transcoder in the GW involved.
In summary, in accordance with the preferred embodiment of the present invention, calls can be optimally routed via an IP network. As such, the existing problems related to tromboning can be successfully resolved. This solution is amplified in an IP-based BSS, because no switching of circuits is needed. Instead of setting up switches to re-direct a call, the BTSs can be informed about the new destination addresses. The IP network then routes the packets via the new destination addresses. In a circuit-switched environment, a BSC would need to know exactly which switches to operate in the network involved (i.e., the network topology has to be known). An RNS does not need to know the topology of an IP network.
Although a preferred embodiment of the method and apparatus of the present invention has been illustrated in the accompanying Drawings and described in the foregoing Detailed Description, it will be understood that the invention is not limited to the embodiment disclosed, but is capable of numerous rearrangements, modifications and substitutions without departing from the spirit of the invention as set forth and defined by the following claims.
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|U.S. Classification||370/329, 455/422.1, 370/338, 370/401, 370/331|
|International Classification||H04L12/56, H04W92/14, H04W80/04, H04W92/12, H04W92/20|
|Cooperative Classification||H04W92/14, H04W92/20, H04W80/04, H04W92/12, H04L45/00|
|Mar 19, 2001||AS||Assignment|
Owner name: TELEFONAKTIEBOLAGET L M ERICSSON (PUBL), SWEDEN
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:MUSIKKA, NIILO;LINDEN, LARS;RINNBACK, LENNART;AND OTHERS;REEL/FRAME:011588/0086;SIGNING DATES FROM 20010115 TO 20010116
|Apr 27, 2009||FPAY||Fee payment|
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|Mar 14, 2013||FPAY||Fee payment|
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